Olefin polymerization catalysts are of great use in industry. Hence, there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties.
Catalysts for olefin polymerization are often based on cyclopentadienyl transition metal compounds as catalyst precursors, which are activated either with an alumoxane or with an activator containing a non-coordinating anion.
A typical metallocene catalyst system includes a metallocene catalyst, a support, and an activator. Supported catalyst systems are used in many polymerization processes, often in slurry or gas phase polymerization processes. For example, U.S. Pat. Nos. 6,846,770 and 6,664,348 disclose catalyst compositions containing at least one metallocene, and least one activator and a support that has been fluorided using a fluoride containing compound and their use in the Examples to make polypropylene in a slurry process. U.S. Pat. Nos. 6,846,770 and 6,664,348 do not address a particular combination of metallocenes and fluorided support where the first metallocene is a monocyclopentadienyl transition metal compound and the second metallocene is a biscyclopentadientyl transition metal compound.
WO 05/075525 describes supports for metallocene catalyst systems of inorganic oxides treated with a fluorinated functionalizing agent, for example, diethylaluminium fluoride.
U.S. Publication No. 2002/007023 describes alumina supports treated with ammonium bifluoride or perfluorohexane which are used with metallocenes and organoaluminium compounds for the polymerization of olefins.
WO 2003/025027 describes fluorided metal oxides as supports for phosphinimine/aluminoxane polymerization catalyst systems.
U.S. Publication No. 2005/0288461 describes fluorided silica/alumina supports for metallocene/organoaluminium catalyst systems. The supports are pretreated, for example, with ammonium bifluoride.
U.S. Publication No. 2014/0031504 discloses examples of dimethylaluminium fluoride treated silica combined with activator of [N(H)Me(C18-22H37-45)2][B(C6F5)3(p-OHC6H4)] and catalyst compound of (C5Me4SiMe2N′Bu)Ti(η4-1,3-pentadiene) to copolymerize ethylene and hexene.
Metallocenes are often combined with other catalysts, or even other metallocenes, to attempt to modify polymer properties. For example, U.S. Pat. No. 8,088,867 discloses a polymer blend prepared by the process of combining under solution polymerization conditions: (A) a first catalyst capable of producing a first crystalline polymer having an Mw of 100,000 or less, (B) a second catalyst capable of preparing a second amorphous polymer having an Mw of 100,000 or less and differing in chemical or physical properties from the first polymer under equivalent polymerization conditions, (C) a cocatalyst, activator, scavenger, or combination thereof, and (D) one or more olefins; wherein the polymer blend is formed in-situ, comprises crystalline polymer segments and amorphous polymer segments, and has an Mw of 100,000 or less. The examples at column 98, line 18 et seq, state:
“The catalyst compounds used to produce semi-crystalline polypropylene were rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dimethyl, rac-dimethylsilylbis(2-methylindenyl)zirconium dimethyl, rac-dimethylsilylbis(indenyl)hafnium dimethyl, and rac-1,2-ethylene-bis(4,7-dimethylindenyl)hafnium dimethyl . . . . The catalyst compounds used to produce amorphous polypropylene were dimethylsilyl(tetramethylcyclopentadienyl) (cyclododecylamido)titanium dichloride, dimethylsilyl(tetramethylcyclopentadenyl) (cyclododecylamido)titanium dimethyl, dimethylsilyl(tert-butylamido) (tetramethylcyclopentadienyl)titanium dimethyl . . . .”
Likewise, U.S. Pat. No. 5,516,848 discloses the use of two different cyclopentadienyl based transition metal compounds activated with alumoxane or non-coordinating anions. In particular, the examples disclose, among other things, catalyst compounds in combination, such as Me2Si(Me4C5)(N-c-C12H23)TiCl2 and rac-Me2Si(H4Ind)ZrCl2, or Me2Si(Me4C5)(N-c-C12H23)TiCl2 and Me2Si(Ind2)HfMe2, (Ind=indenyl) activated with activators such as methylalumoxane or N,N-dimethyl anilinium tetrakis(pentafluorphenyl)borate to produce polypropylenes having bimodal molecular weight distributions (Mw/Mn), varying amounts of isotacticity (from 12 to 52 weight % isotactic PP in the product in Ex 2, 3 and 4), and having weight average molecular weights over 100,000, and some even as high as 1,200,000 for use as thermoplastics.
Likewise, two different catalysts have been placed on a support to make polyolefins, typically in gas phase. For example, U.S. Pat. Nos. 4,701,432 and 5,077,255 relate to olefin polymerization catalyst compositions comprising a metallocene and a non-metallocene impregnated on a support. Further, U.S. Pat. No. 7,141,632 describes supported two catalyst systems used gas phase to produce ethylene hexene copolymers. U.S. Pat. No. 6,207,606 also describes supported dual metallocene catalyst systems useful in gas phase polymerizations.
U.S. Pat. No. 8,598,061, at Examples 7-10 discloses two bis-cyclopentadienyl metallocenes on a fluorided silica-alumina.
Hong et al. in Immobilized Me2Si(C5Me4)(N-t-Bu)TiCl2/(nBuCp)2ZrCl2 Hybrid Metallocene Catalyst System for the Production of Poly(ethylene-co-hexene) with Psuedo-bimodal Molecular Weight and Inverse Comonomer Distribution, (Polymer Engineering and Science-2007, DOI 10.1002/pen, pages 131-139, published online in Wiley InterScience (www.interscience.wiley.com) 2007 Society of Plastics Engineers), disclose (C5Me4)(N-t-Bu)TiCl2/(nBuCp)2ZrCl2 supported on silica used to make ethylene-hexene copolymers where the polymerization rate drops over a short time.
U.S. Publication No. 2012/0130032 discloses a supported monocyclopentadienyl catalyst composition (e.g., SiMe2(C5Me4)(NtBu)Ti eta-4-1,3-pentadiene) for use in gas phase polymerization to make ethylene hexene copolymers.
U.S. Pat. No. 7,192,902 at example 6 discloses preparation of polypropylene using SiMe2(C5Me4)(NtBu)TiCl2/MAO and SiMe2(2-Me-4-Ph-indenyl)2ZrMe2/trispertluorophenylboron on a silica support. Example 3 discloses silica support treated with ammonium hexatluorosilicate and calcined at 500° C. The catalysts appear to be activated in sequence.
U.S. Pat. No. 8,110,518, discloses preparation of various fluorided silica or silica-alumina supports, which are eventually used for propylene (co)polymerization with various biscyclopentadienyl transition metal compounds. Also, U.S. Pat. No. 8,110,518 discloses preparation of fluorided silica-alumina support in a water slurry with NH4F.HF.
Activators useful in metallocene polymerization have also been modified in an attempt to improve the catalyst systems. For example U.S. Pat. No. 7,355,058 discloses catalysts containing haloaluminoxane compositions, where the halogen is fluorine, chlorine, and/or bromine, and is present at about 0.5 mole % to about 15 mole % relative to aluminum atoms.
Other references of interest include: U.S. Pat. Nos. 5,382,630; 5,382,631; 8,575,284, 6,069,213; Kim, J. D. et al., J. Polym. Sci. Part A: Polym Chem., 38, 1427 (2000); ledema, P. D. et al., Ind. Eng. Chem. Res., 43, 36 (2004); U.S. Pat. Nos. 6,656,866; 8,815,357; U.S. Publication No. 2014/0031504; U.S. Pat. Nos. 5,135,526; 7,385,015; WO 2007/080365; WO 2012/006272; WO 2014/0242314; WO 00/12565; WO 02/060957; and WO 2004/046214.
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve increased activity or specific polymer properties, such as high melting point, high molecular weights, to increase conversion or comonomer incorporation, or to alter comonomer distribution without deteriorating the resulting polymer's properties.
It is therefore also an object of the present invention to provide novel supported catalysts systems and processes for the polymerization of olefins using such catalyst systems.
The supported multiple-metallocene catalyst systems described herein address these needs by producing multimodal polyethylene containing an ultra-high Mw (greater than 1,000,000 g/mol), high short-chain branching (SCB) component, that when formed into a film has improved properties (such as toughness, stiffness and or processability).